net/e1000: fix crash with link status in secondary process

The code to update link status is not safe in secondary process.
If called from secondary it will crash, example from dumpcap:

    /dpdk/app/dpdk-dumpcap -i 0000:00:04.0
    File: /tmp/dpdk-dumpcap_0_0000:00:04.0_20240723020203.pcapng
    Segmentation fault (core dumped)

Fixes: 8058034 ("e1000: support EM devices (also known as e1000/e1000e)")
Cc: stable@dpdk.org

Signed-off-by: Jun Wang <junwang01@cestc.cn>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>

drivers/net/e1000/em_ethdev.c

@@ -1136,6 +1136,9 @@ eth_em_link_update(struct rte_eth_dev *dev, int wait_to_complete)
 	struct rte_eth_link link;
 	int link_up, count;
 
+	if (rte_eal_process_type() != RTE_PROC_PRIMARY)
+		return -1;
+
 	link_up = 0;
 	hw->mac.get_link_status = 1;